The invention relates to conveyors in general, and more particularly to improvements in belt conveyors. Still more particularly, the invention relates to improvements in belt conveyors of the type wherein the convexly curved radially outermost portion of a flat belt is reinforced by a bead and is guided by rolling elements.
German Pat. No. 2 055 682 discloses a conveyor wherein the reinforcing member for the outer marginal portion of the belt is a bead which has a slot for the marginal portion of the belt and is caused to advance between pairs of conical rolling elements. The axes of the rolling elements are inclined with reference to the plane of the belt, and the rolling elements of each pair engage opposite sides of the slotted bead for the marginal portion of the belt. Such inclination of the rolling elements is intended to ensure that the bead is subjected to pronounced deforming stresses, namely to the action of forces which tend to narrow the slot and to urge the internal surfaces of the bead against the respective lateral surfaces of the confined marginal portion of the belt. This should establish a self-locking action between the bead and the belt but should not affect the fasteners which are used to secure the bead to the belt. Moreover, the rolling elements are supposed to cause the bead to center the belt and to otherwise act upon the belt in such a way that the magnitude of forces acting upon one lateral surface of the belt matches the magnitude of forces which act upon the other lateral surface of the belt.
The threads or like fasteners which are used to connect the belt to the bead are located between the radially outermost portion of the belt and those portions of the bead which are engaged by the rolling elements. Therefore, if the belt is subjected to pronounced tensional stresses which act radially inwardly, such stresses tend to extract the marginal portion from the slot of the bead. This, in turn, causes the bead to widen the open side or end of its slot with attendant pronounced deformation which leads to rapid destruction of the reinforcing member. The forces which develop in response to the application of radially inwardly oriented tensional stresses to the belt (e.g., as a result of overloading) cannot be readily defined and, therefore, it was considered to be difficult to plain impossible to undertake effective remedial steps.